Off-grid, RV & cabin
Enter your daily load and trailer dimensions. Get your panel wattage, battery size, and whether it actually fits your roof.
How it works
Step 1
A tiny house typically runs a fuller appliance set than an RV used only for travel.
Step 2
This checks whether your required panel array actually fits the available space.
Step 3
Know immediately if you need a ground mount or load reduction before buying panels.
For a 3,500Wh daily load covering a fridge, lighting, a laptop, an induction cooktop, and other daily use, roughly 875 watts of solar covers the load at 5 peak sun hours. A 26 by 8.5 foot trailer roof, after accounting for vents and an AC unit, comfortably fits this array with room to spare. For the official wording, see the NREL's PVWatts solar calculator. An off-grid system lives or dies on upkeep. The annual maintenance cost estimator in our Maintenance & Lifespan section can help you plan cleaning and inspection costs over the years.
Higher daily loads or lower sun hour regions can push required panel wattage beyond what a small trailer roof can physically fit, especially after subtracting space for AC units, vents, and skylights. In that case, a ground-mounted array, load reduction through more efficient appliances, or accepting a smaller solar contribution supplemented by a generator or other power source becomes necessary. The DOE's solar photovoltaic technology basics keeps the current program details, and it is worth a look before you decide. The real comparison is against a grid connection. The 25-year lifetime savings calculator in our Savings & Payback section can help you weigh the system cost against what the grid would charge.
A 26 by 8.5 foot trailer roof has about 221 square feet total, but obstructions like roof vents, an AC unit, and skylights commonly reduce usable panel space to around 190 to 200 square feet, enough for roughly 3,200 to 3,400 watts of modern panels. This is comfortably more than most full-time tiny house loads require, though larger loads or more obstructions can tighten that margin considerably.
A full-time tiny house typically runs a fuller set of daily appliances, including cooking equipment and sometimes a washer, compared to an RV used intermittently for travel, which pushes daily load and required solar meaningfully higher despite similar physical dimensions. Treating a tiny house's power needs like an RV's is a common sizing mistake that leaves the system undersized for genuine full-time living. Federal tax treatment applies to tiny house solar systems too, and it's worth checking the federal ITC calculator in our rebates and incentives tools before finalizing a budget.
Run the tiny house battery sizing calculator for a more detailed battery breakdown, and check the RV roof space calculator if you want to compare against a more travel-oriented use pattern. The roof space vs output estimator in our system sizing tools runs a related calculation from a slightly different angle, and production estimates throughout draw on NREL's PVWatts solar calculator. DOE's solar photovoltaic technology basics is a solid next read if any of the fundamentals here need more background.
Questions
For a 3,500Wh daily load covering a fridge, lighting, a laptop, an induction cooktop, and other daily use, roughly 875 watts of solar covers the load at 5 peak sun hours. A 26 by 8.5 foot trailer roof, after accounting for vents and an AC unit, comfortably fits this array.
Higher daily loads or lower sun hour regions can push required panel wattage beyond what a small trailer roof can physically fit, especially after subtracting space for AC units, vents, and skylights. In that case, a ground-mounted array, load reduction, or accepting a smaller solar contribution supplemented by other power sources becomes necessary.
A 26 by 8.5 foot trailer roof has about 221 square feet total, but obstructions like roof vents, an AC unit, and skylights commonly reduce usable panel space to around 190 to 200 square feet, enough for roughly 3,200 to 3,400 watts of modern panels.
A full-time tiny house typically runs a fuller set of daily appliances, including cooking equipment and sometimes a washer, compared to an RV used intermittently for travel, which pushes daily load and required solar meaningfully higher despite similar physical dimensions.
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